Acid dyes applied to polyamide, nylon and wood fibers have a tendency to dye at the point of initial contact. The rapid reaction between the dye and the fiber at the point of initial contact, can cause an uneven appearance or coloration to develop in the dyed fiber. This problem can be exacerbated when several dyes are used to produce a desired shade on the fiber, typically compounding the uneven coloration problem. In addition, the dyes may react at different rates to produce a separation of colors on the fiber. To alleviate this problem, a variety of materials, so-called "dye-leveling agents", have been used to produce a level dye application. These dye-leveling agents, are typically surfactants selected from anionic, cationic, nonionic, and amphoteric classes of surfactants, with anionic being the most common form.
Thus, dye leveling agents are used in the process of dyeing fibers, such as nylon, wool and silk in order to give an even coverage by the dye on the fiber being dyed. Anionic surfactants such as alkyl diphenyloxide disulfonate (commercially available under the trademark DOWFAX 2A-1, a product of Dow Chemical Corp.), are typically used as leveling agents. An inherent disadvantage of using these products is that they tend to be poor wetters and high foamers. The wetting ability of the dye bath is particularly important when dyeing nylon fibers which have been treated with a fluorochemical. To alleviate these wetting and foaming problems, auxiliary wetting agents and defoaming agents are typically added to the dye bath. In addition to the cost of these auxiliary agents, their use can increase the chance of mixing and measuring errors, as well as increase the inventory requirement of chemicals needed either as part of the mixing operation or to correct measurement errors that occur.
A common problem encountered when dyeing natural and/or synthetic fibers, such as wool fibers or polyamide fibers, is the tendency of the dye to provide uneven coloration of the fiber. In essence, the dye more rapidly reacts at the point of initial contact with the fiber, thus giving an uneven appearance to the dyed fiber. This problem is accentuated when several dyes are utilized to produce a desired shading on the fiber. For example, the dyes may react at different rates to produce a separation of colors, causing a variation in shading at different points along the fiber and resulting in what is commonly referred to as "poor shade depth".
To alleviate the above problems, various materials have been suggested in the past to provide level fiber dyeing. These materials, commonly referred to as "dye-leveling agents", have in the past frequently contained anionic surfactants, such as alkyl diphenyloxide disulfonate. By way of illustration, alkyl diphenyloxide disulfonate has been used commercially as an acid dye-leveling agent. However, this disulfonate has the disadvantage of providing higher foaming and poorer wetting (as measured by a draves wetting test) than might be desired, as well as being limited in its usefulness to a relatively narrow pH range. In addition, as demonstrated in Comparative Example A, at column 8, lines 55-67 of U.S. Pat. No. 5,030,245, a dye-leveling agent consisting essentially of such an alkyl diphenyloxide disulfonate (which in that example was DOWFAX 2A-1 alkyl diphenyloxide disulfonate, a product of Dow Chemical Company), did not result in a full dye shade development in the dyeing of nylon carpet. Further, alkyl diphenyloxide disulfonate surfactants such as DOWFAX 2A-1 surfactant tend to contribute to poorer fiber wetting by the dye bath composition and higher foaming in the dye bath than otherwise might be desired. Accordingly, the search has continued for improved dye-leveling compositions that do not suffer from these poor wetting and high foaming problems.
The prior art is replete with various attempts to provide good dye-leveling agents to the carpet dyeing industry. By way of illustration, the above-mentioned '245 patent discloses a combination dye-leveling agent/stainblocker comprising a polycarboxylated linear alcohol alkoxylate as the dye-leveling agent and a sulfonated phenolformaldehyde diphenylsulfone condensate as the stainblocker, alone or together with an alkoxylated linear alcohol alkoxylate as a wetting agent. Although these compositions provide good dye-leveling in use with acid dyestuffs, there is still a need in the dyeing industry for further improvement.
U.S. Pat. No. 3,684,426 describes alkyl diphenylether disulfonate together with an ethoxylate quaternary ammonium compound as pretreatment for improved dyeing of synthetic polyamide fibers.
Although various salts of hydroxylamine, such as hydroxylammonium nitrate (so-called "HAN"), which is the nitrate salt of hydroxylamine, are known, their use in the dyeing industry is not known to the knowledge of the present inventors. HAN is an excellent insensitive oxidizer for propellants, as disclosed, for example, in U.S. Pat. No. 4,968,394, the disclosure of which is more specifically directed to a method for reducing excess nitric acid in aqueous hydroxylamine nitrate solutions.
U.S. Pat. No. 3,592,584 discloses a dyeing composition for polyamide fibers comprising a combination of a premetallized dye and a dyeing assistant selected from the group consisting of dodecylbenzene sulfonic acid, diethanolamine, and disodium dodecyldiphenylether disulfonate. However, these compositions have proved less effective in providing streak-free, even dyeings of fibers than might be desired.
New dye-leveling compositions that are low in foaming and provide good fiber wetting, and are useful in facilitating level dyeing and good shade depth development during the fiber dyeing process, would be highly desired by the fiber dyeing community. If such new dye-leveling agents are usable in conjunction with a wide variety of dyestuffs for dyeing a variety of natural and synthetic fibers, such as wool, silk, and polyamide, these dye-leveling agents would be particularly advantageous to the fiber dyeing industry.
Recently, a solution to this dye-leveling problem has been proposed using the reaction product of a piperazine compound with an alkyl diphenyl ether sulfonic acid, as-described in U.S. Pat. No. 5,360,457. Likewise, certain 2-piperazinones (which contain keto-substitution on the ring) are disclosed in compositions containing alkylated diphenyl oxide sulfonate surfactant, alone or in combination with a nonionic surfactant that may contain a mixture of ethoxylated and propoxylated alcohol, as taught in U.S. Pat. No. 5,196,146. The '146 patent focuses upon hard surface cleaner compositions for cleaning grease and oil from metal, plastic, and glass, all material that are not subject to the dye leveling problem encountered by the fiber dyeing industry.
The present invention provides another solution to this dye leveling problem for the fiber industry.